Penguin had led 8-4 at one stage in the second period but were then hit by a rapid five-goal response from Poly. It was 10-9 to Poly three minutes from the end of the third quarter, prompting a rally from Penguin, who charged into a 13-10 lead.
Poly had recovered to trail 13-12 with three minutes to go, setting up a nervy finale in which both sides failed to convert man-up opportunities. Claudio Bagnoli (5) and Bence Kadar (3) dominated the Penguin scoring. The main goal threat from Poly came from Chris Brown (5) and Chris Icely (4).
Late goals by Callum Bailey (2) and Jack Waller clinched an 11-8 victory for Invicta over Sutton & Cheam.
Picture (by Trevor Hyde): Penguin's Claudio Bagnoli.